Resistor - Capacitor - Resistor

In summary, the conversation discusses the order of resistors in a series circuit and how it affects the voltage measurement across a capacitor. The first question asks if both resistors are in series during the charging interval, and the response explains that they can be combined if only considering the voltage across the capacitor. However, if considering the voltage between the capacitor and Earth, the order of the resistors would change. The second question asks for clarification on this concept, and the response explains that the phase of the voltage between the positive end of the capacitor and Earth will not be the same as the phase of the voltage between the ends of the capacitor. This is due to the reference point from which the voltage is measured. There is no charge loss in
  • #1
Sefrez
126
0
This should be a simple question.

If you have a series circuit in the following order: emf, resistor1, capacitor, resistor2

Are both resistors in series during the charging interval considering that they both have the same current through them? That is, would a resistance of resistor1 + resistor2 either before or after the capacitor be equivalent?
 
Physics news on Phys.org
  • #2
If you are only considering the voltage across the capacitor then you can combine the two resistors. BUT NOT if you are considering the voltage between the 'top end' of the capacitor and Earth, for instance. For that, you need to do things in a different order.
 
  • #3
I believe I am speaking of the first you mention. For the second, could you explain in a little more detail what that would be? The way I am picturing it now is that your saying the wire at which terminates at the negative terminal of the emf is earthed. Is that correct? If so, how does this change the situation? Charge loss or something?

Thanks!
 
  • #4
I had to stop and think there!
The problem was that you didn't actually ask the question which answered! (HAHA - very common)
I was initially talking in terms of measuring volts in the AC situation but the same must apply to the transient waveform at switch on. The current flow with time will be the same (defined by R(total) and C) but, with the resistance 'split' across the C, the voltage at the top of the C will start at Vin, modified by the potentiometer ratio to a value above zero and end up at Vin. Think of it this way: if the top resistor were nearly zero, the value of PD to Earth would be nearly Vin all the time.

There is no "charge loss". The difference is the reference point from which you would be measuring the 'output' PD.

If the capacitor is 'in the middle' then the phase of the PD between positive end of the capacitor and Earth will not be the same as the phase of the PD between the ends of the capacitor. (wrt the phase of Vin)
 
  • #5


Yes, both resistors would be in series during the charging interval because the current flows through both of them in a single path. This means that the total resistance in the circuit would be the sum of resistor1 and resistor2. Therefore, a resistance of resistor1 + resistor2 before or after the capacitor would be equivalent.
 

FAQ: Resistor - Capacitor - Resistor

1. What is the purpose of a resistor-capacitor-resistor (RCR) circuit?

An RCR circuit is commonly used to filter out unwanted noise or signals from a circuit. It can also be used to shape the frequency response of a circuit or to create a time delay.

2. How does a resistor-capacitor-resistor circuit work?

In an RCR circuit, the first resistor limits the current flow while the capacitor stores and releases charge. The second resistor then controls the discharge rate of the capacitor, creating a smooth output signal.

3. What is the difference between a resistor-capacitor-resistor circuit and a resistor-capacitor (RC) circuit?

The addition of the second resistor in an RCR circuit allows for more precise control over the discharge rate of the capacitor, resulting in a more stable and accurate output signal. In an RC circuit, the discharge rate is solely dependent on the value of the first resistor.

4. How do I choose the values for the resistors and capacitor in an RCR circuit?

The values of the resistors and capacitor in an RCR circuit are dependent on the specific application and desired output. Factors to consider include the frequency of the input signal, the desired frequency response, and the time delay required.

5. Can an RCR circuit be used in both AC and DC circuits?

Yes, an RCR circuit can be used in both AC and DC circuits. In AC circuits, the capacitor charges and discharges at a certain frequency, while in DC circuits, the capacitor charges and discharges continuously. However, the values of the resistors and capacitor may differ between AC and DC circuits.

Back
Top